PROJECT SUMMARY/ABSTRACT Gay and bisexual men (GBM), and other men who have sex with men continue to account for a significant majority of all new HIV infections in the U.S, with condomless anal sex in the absence of PrEP being the most common HIV transmission risk behavior (TRB). An HIV syndemic has been identified that consists of several epidemics have high levels of comorbidity and work synergistically to increase TRB. These syndemic factors include polydrug use, sexual compulsivity, depression, intimate partner violence, and childhood sexual abuse. Understanding the mechanisms that drive the associations between syndemic factors and TRB is important in developing effective interventions for reducing the HIV burden in this population. The primary goal of this dissertation is to examine three potentially linking mechanisms: emotion regulation, executive attention, and attentional bias. Based on existing research, we hypothesize that these three mechanisms serve as mediators of the associations between syndemic factors and TRB. This R36 dissertation proposal has two aims: (1) Examine the role of emotion regulation and executive attention on the associations between experiences of victimization, drug use, depression, sexual compulsivity, and TRB, and (2): Examine attentional bias for drug- related and sex-related cues and the influence of attentional bias on the associations between drug use, sexual compulsivity, and TRB. To test these aims, we will assess syndemics, emotion regulation, executive attention, attention bias, and TRB in an ongoing NIDA-funded study of syndemics among 1,071 GBM from across the U.S. We will also examine these mechanisms in an original sample of 90 HIV-negative GBM in New York City stratified by sexual compulsivity and polydrug use. The findings from this dissertation study will inform the development of interventions to reduce the burden of HIV among GBM as well as future research. The ultimate goal of this dissertation grant is to launch Mr. Moody?s career as an independent clinical researcher focused on the intersection between substance use, sexual risk behaviors, and mental health among GBM.